1. Field of the Invention
The present invention relates to a thin-film magnetic head with a heating means, a head gimbal assembly (HGA) with the thin-film magnetic head and a magnetic disk drive apparatus with the HGA.
2. Description of the Related Art
In a magnetic disk drive apparatus, when writing or reading signals, a thin-film magnetic head (slider) hydrodynamically flies with a predetermined spacing (flying height) on a rotating magnetic disk. While flying on the magnetic disk, the thin-film magnetic head writes signals to the magnetic disk using magnetic fields generated from an inductive write head element, and reads signals by sensing magnetic fields corresponding to the signals from the magnetic disk with the use of an magnetoresistive (MR) effect read head element. On these cases, a magnetic spacing dMS is defined as an effective magnetic distance between ends of these head elements and the surface of the magnetic disk.
With higher recording density due to increasing data storage capacity and miniaturization of the magnetic disk drive apparatus in recent years, a track width of the thin-film magnetic head is becoming smaller. In order to avoid the degradation of writing and reading performance due to the smaller track width, latest magnetic disk drive apparatuses actually have the magnetic spacing dMS reduced down to the order of 10 nm. In the case, some techniques are proposed, which control the smaller dMS with some accuracy by positively utilizing a thermal pole tip protrusion (TPTP) phenomenon with the use of a heater provided near or inside the magnetic head element, for example, in U.S. Pat. No. 5,991,113, US Patent Publications Nos. 2003/0174430 A1 and 2003/0099054 A1, and Japanese Patent Publication No. 05-020635A.
However, in the thin-film magnetic head with the above-mentioned heater, the amount of protrusion of a trailing portion of an overcoat layer covering the head elements toward the magnetic disk surface due to heat generated from the heater, becomes larger than that of the head end surface adjacent to the end of the head elements. In addition, an air bearing surface (ABS) of the slider is usually inclined so that the trailing portion is closer to the magnetic disk surface. Therefore, the difference between the amounts of these protrusions is likely to cause the protruded trailing portion to contact the magnetic disk surface. As the result, a thermal asperity that is a problem such that the MR read head element outputs abnormal signals due to heat generated by the contact has possibilities to occur. Further, the contact has a risk of causing physical damage or crash of the magnetic head element and the magnetic disk. Moreover, because of the existence of the protruded trailing portion, the head end surface adjacent to the end of the magnetic head element needs to be separated from the magnetic disk surface by a required amount, and therefore, the magnetic spacing dMS can not be efficiently set to an adequately small value.
Furthermore, the thin-film magnetic head with the above-mentioned conventional heater can not adapt to lower electric power consumption of the device mounting the magnetic disk drive apparatus.
Currently, some mobile devices such as a mobile phone are encouraged to mount the magnetic disk drive apparatus because the devices need to deal with large volumes of video data, music data and so on. However, the electric power consumption of the devices must be reduced inevitably, and then, the power supply of the preamplifier for driving the mounted magnetic disk drive apparatus is limited more than ever. Therefore, in the thin-film magnetic head with the above-mentioned conventional heater, the power required for reducing the magnetic spacing dMS to the predetermined value can not be surely supplied to the heater. As the result, the head end surface adjacent to the end of the magnetic head element is not protruded to the required extent, and therefore, sufficient writing and reading performances can not be obtained.